Formula-fed infants present higher cholesterol synthesis rates and lower circulating cholesterol during the postnatal feeding period compared to breast-fed infants, though the mechanisms underlying this phenotype are not fully understood. Typical infant formulas contain vegetable-based fats, inherently including phytosterols (PS), which are structurally similar to cholesterol and may interfere with their absorption. A seven-day old piglets model was used to test the inhibitory effects of PS on cholesterol absorption during postnatal feeding. Following feeding for 21 days with milk-based formulas containing PS and cholesterol levels resembling those in formulas or human-milk, apparent cholesterol digestibility was analyzed in ileal digesta, and cholesterol, PS, and cholesterol synthesis markers were analyzed in plasma and liver samples. Ileal cholesterol digestibility content was increased in the piglets fed low PS formulas and the rate of the hepatic cholesterol synthesis, as determined by the lathosterol-to-cholesterol ratios (L:C), was decreased in the piglets fed LP-formulas and corresponded to reduced nuclear expression of SREBP2 relative to those fed HP-formulas. These results are consistent with the hypothesis that PS in formula can inhibit cholesterol absorption and enhance cholesterol synthesis. Whether or not this leads to entrainment of cholesterol synthesis later in life via early programming awaits further research.
Keywords: absorption; cholesterol; infant formula; plant sterols; synthesis.